Fibromyalgia: What We Know, What We Suspect, What We Don't
A condition once dismissed as unexplained is now one of the best-characterised examples of altered central pain processing.
In brief
- Diagnostic criteria are symptom-based and have been substantially revised.
- Objective differences in pain processing are measurable in group studies.
- Exercise has the most consistent evidence, though initiation must be gradual.
- Small-fibre findings in a subgroup remain an open research question.
Evidence label: Established Evidence — Supported by multiple high-quality trials, systematic reviews, or broad scientific consensus.
How the diagnosis works now
The tender-point examination of the 1990 criteria has been replaced. Current criteria use a widespread pain index and symptom severity scale covering fatigue, unrefreshing sleep, and cognitive symptoms. This reflects a shift in understanding: fibromyalgia is characterised as a disorder of pain regulation, not a disorder of specific tender tissues.
What is measurably different
Group studies consistently show enhanced temporal summation, reduced conditioned pain modulation, and altered functional connectivity involving the insula. Some studies report elevated glutamate in relevant regions. These are group-level findings; none is a diagnostic test.
A subgroup shows reduced intra-epidermal nerve fibre density on skin biopsy, consistent with small-fibre pathology. Whether this represents a distinct subtype, a consequence, or an incidental finding is genuinely unresolved — an example of active, honest uncertainty in the field.
- Enhanced temporal summation of pain
- Reduced efficiency of descending inhibition
- Altered insular connectivity on functional imaging
- Small-fibre findings in a subgroup, significance unclear
What the treatment evidence supports
Exercise — aerobic and resistance — has the most consistent supporting evidence, with the crucial caveat that starting intensity is routinely set too high. Below-threshold starts with very gradual progression outperform ambitious programmes that trigger flares and dropout.
Cognitive behavioural approaches show small to moderate effects on function and distress. Certain medications acting on central mechanisms have regulatory approval; effects are modest, and tolerability is a common limiting factor. Opioids are not recommended.
The most common reason exercise fails in fibromyalgia is that it began at the intensity a healthy person would choose.
Open questions worth watching
Whether autoimmune mechanisms contribute in a subset — suggested by passive-transfer work in animal models — is an active area. So is the role of the gut microbiome, where findings are early and easily overinterpreted. We will update this article as replication arrives, and we will say plainly if it does not.
Common questions
- Is fibromyalgia progressive?
- It is not a degenerative condition and does not damage joints or muscles. Symptom severity fluctuates, and many people improve their function substantially over time.
- Is there a blood test?
- No validated diagnostic test exists. Blood work is used to exclude other conditions, not to confirm fibromyalgia.
References
- 1Wolfe F, et al. 2016 revisions to the 2010/2011 fibromyalgia diagnostic criteria. Seminars in Arthritis and Rheumatism, 2016
- 2Clauw DJ. Fibromyalgia: a clinical review. JAMA, 2014
- 3Goebel A, et al. Passive transfer of fibromyalgia symptoms from patients to mice. Journal of Clinical Investigation, 2021
Written by
Dr. Elena Marsh
PhD, Pain Neuroscience
Elena researches nociplastic pain and threat learning. She writes about what the evidence supports, what it does not, and where the honest uncertainty lies.
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